Those were some of the headlines that ran last Wednesday. By then, the standoff was old news to the hundreds of frenzied commuters caught off-guard Tuesday evening in the backed-up snarl of rush-hour traffic.

Despite the long delays, the five-hour standoff — which resulted in the evacuation of a number of buildings along 15th Street (including The Hill’s offices) and prompted the use of a royal flush of emergency vehicles — ended peacefully. Police found homemade devices, such as wires and a switch, in the van. Shortly after 9 p.m., the van was declared safe and impounded.

That night, Washingtonians went home knowing that the cogs of the Department of Homeland Security had kicked into high gear, with well-oiled efficiency. We were supposed to rest well.

But can we really rest well?

What if the van’s contents had been less benign — had contained a homespun nuclear device? Would things have gone as smoothly? HBO’s new film “Dirty War,” which originally appeared on the BBC and runs through February, suggests that the answer is no.

Directed by Dan Percival and co-written with Lizzie Mickery, the film, which premiered on HBO on Monday, is a docudrama about what would happen if a “dirty bomb” — known as a radiological dispersal device (RDD) — were to go off in downtown London. A dirty bomb “combines a conventional explosive, such as dynamite, with radioactive material,” according to the U.S. Nuclear Regulatory Commission.

The film opens in the middle of a decontamination drill in central London. We meet two of the main characters: a civil servant (Helen Schlesinger) in charge of making sure that London is prepared for radiological attacks, and a fireman (Alastair Galbraith) whose crew is being trained to deal with an attack. Not surprisingly, they have polar-opposite opinions of how well the test goes. A lovely, clich�d scene ensues, with the fireman publicly berating the minister for not telling the public the truth: London is unprepared.

At this point, you have a good idea of what’s coming, but I’ll run through it anyway: Islamic extremists are plotting to blow up London, a team of investigators is tracking various different terror cells (conveniently explaining how the cells work as they proceed), terrorists are successful, safety measures don’t work, chaos ensues and downtown London becomes a nuclear wasteland.

The final shot shows the wife of the fireman from Scene 1 — who sacrificed himself to save people at “ground zero” — riding home on a bus past the now fenced-off streets surrounding the attack.

A few less of these tidy, formulaic moments and the film really could have been brilliant — much darker and more disturbing. Unfortunately, Percival and Mickery seem to favor all things ironic and politically correct. The investigator who discovers the cell is not only a woman, she’s Muslim and superdiligent. The fireman who intends to quit his job goes in one last time. And it is, of course, the nosy neighbor who gives the investigation team the tip it needs to solve the case.

The show is still worth seeing. It is well-written and carefully researched, courtesy of the BBC fact department. And plenty of real-life material drives the plot, which makes the film seem both eerily familiar and uncomfortably believable. Uncomfortable in the sense that you don’t want it to be depicting the truth, but you suspect that it likely is.

For example, after the attack, millions of people flood the streets. Their collective state of mind: scared, confused and contaminated. The absolute worst thing they can do is to go home untreated, which is why central command tries to cordon off the area to keep people from getting out. After last Tuesday’s traffic jam, it’s not hard to imagine just how daunting (and unsuccessful) such a task is.

As a public-service announcement (which, in some ways, the film is meant to be), “Dirty War” is certainly a gripping piece of propaganda for the Department of Homeland Security — you don’t leave questioning security spending.

“Dirty War” is the first of a series of three movies done in partnership by HBO and PBS. “Sometimes in April,” about the 1994 Rwandan genocide, will be released in March on HBO and in April on PBS, and “Yesterday,” about AIDS in South Africa, will be coming out later this year. Future screenings of “Dirty War” will be on HBO on Jan. 27, Feb. 2 and Feb. 7.